Homeostatic regulation of dendritic dynamics in a motor map in vivo

Neurons and circuits are remarkably dynamic. Their gross structure can change within minutes as neurons sprout and retract processes to form new synapses. Homeostatic processes acting to regulate neuronal activity contribute to these dynamics and predict that the dendritic dynamics within pools of neurons should vary systematically in accord with the activity levels of individual neurons in the pool during behavior. Here we test this by taking advantage of a topographic map of recruitment of spinal motoneurons in zebrafish. In vivo imaging reveals that the dendritic filopodial dynamics of motoneurons maps onto their recruitment pattern, with the most electrically active cells having the lowest dynamics. Genetic reduction of activity inverts this map of dynamics. We conclude that homeostatic mechanisms driven by a gradient of activity levels in a pool of neurons can drive an associated gradation in neuronal dendritic dynamics, potentially shaping connectivity within a functionally heterogenous pool of neurons.